#include <iostream> 
using namespace std;

int main()
{
long long a;
long long b;
long long n;

long long weeks;
long long days=0;
long long today=0;
cin >>a>>b>>n;
weeks=n/(5*a+b*2);
n-=weeks*(5*a+b*2);
while(n>0){

if(today<5)
{
	n-=a;
}
else
{
	n-=b;
}
today++;
today%=7;
days++;
}
cout<<weeks*7+days<<endl;
	return 0;
}
